If the email to the other person who posted in the thread wasn't enough, I also finally received official word
I don't know if EF orders their stuff directly from Standard Innovations, or from a distributor. If it's from a distributor then EF may be able to get more in if the distributor has it still in stock. So even though it is now out of stock again, doesn't exactly mean they won't get more in.
SI/WeVibe actually sent me a case of them because I wanted to do a blog giveaway; they only had Red left, they were actually clean out of black and white forever.
I own both Salsa and Tango and have never, ever been able to discern any sort of vibration difference between the two models. I think that if someone CAN, then perhaps their less-powerful model is defective. I confirmed with SI that the motors and everything are utterly identical from Salsa to Tango.